Commercial paper products such as hand towels are manufactured from cellulosic base sheets. A cellulosic base sheet is a paper product in its raw form prior to undergoing post-treatment such as calendaring and embossing. In general, cellulosic base sheets are made by preparing an aqueous suspension of papermaking fibers and depositing the suspension onto a sheet-forming fabric to form a wet web, which is then dewatered and dried to produce a base sheet suitable for finishing.
Wet web base sheets are commonly dried by through-air drying, which comprises removing water from a wet web by passing hot air through the web. More specifically, through-air drying typically comprises transferring a partially dewatered wet-laid web from a sheet-forming fabric to a coarse, highly permeable through-drying fabric. The wet web is then retained on the through-drying fabric while heated air is passed through the web until it is dry. One process for through-drying base sheets is the Un-Creped Through Air Dried (UCTAD) process, as described, for example, in U.S. Pat. No. 6,149,767, which is hereby incorporated by reference. In the UCTAD process, a wet base sheet is partially dewatered and through-air dried by passing hot air through the wet sheet as it runs over a through-drying fabric on a drum roll.
Based upon consumer complaints, it was observed that a strong, burnt popcorn odor was often emitted from hand towels when the towels were wetted. Upon investigation, this problem of malodor was found to be present in cellulosic base sheets which had been through-air dried at relatively high air temperatures including, for example, sheets dried by the UCTAD process. It was hypothesized that over-drying or over-heating of the base sheets was leading to the malodor problem upon re-wetting. Thus, by operating the through-air drying process at lower temperatures and slightly longer residence times, the malodor problem has largely been eliminated. However, lower operating temperatures and longer residence times adversely affect the overall productivity of the base sheet manufacturing process. Therefore, a need exists for a process which can eliminate malodor in through-dried cellulosic base sheets wherein higher drying temperatures and shorter residence times can be used to increase product throughput and productivity.